Manufacture of tubes



Dec. 8, 1936. 3 w, UTTLE 2,063,689

MANUFACTURE OF TUBES Filed July 3, 1933 3 She ets-Sheet l INVENTORS Dec.8, 1936. 1 c. w. LITIILER 2,063,689

MANUFACTURE OF TUBES Filed July 5, 1935 s Shets-Sheet '2 INVENTORS Dec.8, 1936. HTTLER 2,063,689

MANUFACTURE OF TUBES Filed July 5, 1933 3 Sheets-Sheet 3 Patented Dec.8, 1936 PATENT OFFICE MANUFACTURE OF TUBES Carl W. Littler, Pittsburgh,Pa., assignor to Jones & Laughlin Steel Corporation, Pittsburgh, Pa., acorporation of Pennsylvania Application July 3, 1 933, Serial No.678,808

20 Claims.

This invention relates to the manufacture of tubes, and moreparticularly to the manufacture of seamless tubes having relatively thinwalls. It relates still more particularly to the manufacture of smalldiameter tubes such as are used in boilers, stills, etc.

The invention further relates to manufacture of tubes having relativelysmall diameters and relatively thin walls by performing a part of theoperation on a push bench. In the push bench process of tube manufacturea heated billet is pierced in a press throughout the greater portion ofits length to form a bottle which is then placed over the nose of amandrel and pushed thereby. through a series of aligned dies to thin andelongate the bottle over the mandrel to form a tube blank. The pushbench has certain distinct advantages among which are that the operationmay be performed economically at high speed and that a quality of steelmay be used in a push bench which would be entirely unsatisfactory foruse in the formation of tubes by the piercing process.

However, the push bench process has certain limitations as to the wallthickness, length and diameter of tubes formed thereby. Particularlywith respect to wall thickness a limitation is imposed by reason of thefact that the great pressures exerted on the blank when it is pushedthrough the dies inthe push bench place the metal under great tensilestress and tend to tear it. Therefore it isnot practicable to formextremely thin walled tubing on a push bench.

It has heretofore been proposed to form a rela tively short thick walledblank in a push bench and then, after stripping, to pass the samethrough a reducing mill to reduce the diameter and increase the length.However, as the tend- .ency of a reducing mill is to increase, ratherthan reduce, the wall thickness, this method is not satisfactory for theproductionof thin walled tubing.

Thin walled tubing can be very satisfactorily and economicallymanufactured by first forming on a push bench a relatively short thickwalled tube blank and thereafter elongating said blank and thinning itswall over a mandrel. The elongating and thinning operation performedsubsequently to the push bench operation is preferably carried out bypassing the blank having a mandrel therein through an elongator betweencross rolls which simultaneously thin and elongatethe blank'over themandrel and loosen the blank on the mandrel so that it may easily bestripped. This is a consideration of some consequence as the problem ofstripping assumes dim culty when the wall thickness of the blank isconsiderably reduced.

The mandrel emerging from the push bench and having thereon the blankwhich has been 5 thinned and elongated in the push bench may be passedimmediately through an elongator wherein the blank is further thinnedand elongated over the same mandrel and at the same time loosened tofacilitate stripping; or the blank may first be stripped from the pushbench mandrel, preferably after having been loosened by a reeler, andmay then, with or without reheating, have another mandrel introducedthereinto and the subsequent elongation performed over the secondmentioned mandrel. In the latter case. the second mentioned mandrel maybe of materially less diameter than the push bench mandrel, this beingparticularly desirable when relatively small diameter tubing is to beformed. In such case the elongator spins and reduces the blank about thesmaller mandrel and at the same time reduces its Wall thickness. Theclosed end of the blank emerging from the push bench may be sawed orcropped off at any time during 5 the operation either before or afterreheating or passing the same through the elongator.

The blank emerging from the elongator has the elongator mandrel removedtherefrom, this being rendered relatively easy by reason of theloosening action of the elongator, and suchblank may then be passed toand through a reducing mill to further reduce the diameter of the blankand further elongate it. This additional step. is highly desirable inthe manufacture of tubing of extremely small size. The preceding passageof the blank through the elongator is particularly well adapted toprepare the blank for passage through the reducing mill, as the reducingmill has a tendency to slightly increase the wall thickness of theblank, whereas the elongator is particularly well adapted for reducingwall thickness, and therefore the wall thickness may be reduced in theelongator to such a point that after passage of the blank through thereducing mill, with the attendant slight increase in Wall thickness, thedesired ultimate wall thickness will be obtained. Furthermore, the useof the elongator enables doing away with several passes of there'clucingmill, particularly if the elongator mandrel is materially smaller insize than the push bench mandrel, a single pass through the elongatorbeing capable of accomplishing the work of several passes through thereducing mill. 5

More than one elongator pass may be utilized if desired, although onaccount of the relatively great amount of work capable of beingperformed in a single elongator pass one pass will be sufficient formost ordinary purposes. In the manufacture of tubing of minimum wallthickness more than one elongator pass may be desirable.

Certain particular advantages arise by reason of the passage of a blankthrough an elongator after formation in a push bench. Sometimes theblanks formed on the push bench tend to have a somewhat uneven wallthickness, and the elongator tends to reduce any eccentricity andincrease the uniformity of the wall thickness. This is probably broughtabout by reason of the spinning action in the elongator.

Other details, objects and advantages of the invention will becomeapparent as the following description of certain present preferredembodiments thereof proceeds.

In the accompanying drawings I have shown certain present preferredembodiments of the invention, wherein Figure 1 is a diagrammatic planview of a portion of a tube mill;

Figures 2A and 2B taken together constitute a diagrammatic plan view ofa portion of a tube mill of modified design; and

Figure 3 is a diagrammatic plan view of a reducing mill.

Referring more particularly to Figure 1, reference numeral 2 designatesgenerally a push bench, the particular portion of the bench being shownbeing simply the conveyor or runout table carrying the blank with themandrel therein after passing through the dies. As no specificimprovement in the push bench per se is herein described or claimed, thepurely diagrammatic representation of the push bench by its runout tablewill sufiice for the drawings.

Reference numeral 3 designates generally an elongator which comprisescross rolls 4 suitably mounted for rotation and having their facesdesigned to materially thin and elongate the wall of the blank over themandrel. The cross rolls are driven by a motor 5 through gearing B anddriving connections 1. Guides 8 insure proper alignment of the mandreland blank and proper introduction thereof into a passage thereof throughthe elongator. A conveyor 9 also assists in advancing the mandrel andblank to the elongator. The mandrel and blank may be advanced either bythe provision of driving means for at least some of the conveyor rollsor in any other well known manner.

The elongator 3 materially thins and elongates the blank over themandrel additionally to the thinning and elongation accomplished in thepush bench. Even though a relatively cheap quality of steel is used forthe push bench operation, the latter seems to have the efiect ofconsolidating and solidifying the metal at least to such an extent as topermit of relatively heavy reductions in the elongator. It is possiblein the elongator to increase the length of the blank to from two to fivetimes its original length or more, the setting of the elongator beingordinarily determined by the length of the mandrel and the particularproduct desired.

The blank and mandrel after leaving the elongator pass along a runouttable from which they are lifted by fingers H and transferred laterallyon rails 12 to a roller conveyor l3 which moves the same to the leftinto cooperative relationship with a stripper l4, which may be of anydesired or well known construction and which pulls out thelmandrel, theblank remaining in place against a stop. The blank is then lifted out ofthe conveyor l3 by fingers l and passes laterally along rails I6 toanother roller conveyor I! which advances the blank to the left throughguides l8 and I8 until its forward end rests upon a roller conveyor 20.The rear end of the blank is positioned to have its closed extremitysawed off by the rotary saw 2|. If desired the front end of the blankmay also be sawed oil.

fIhe blank on the conveyor 20 after one or both of 'its ends have beensawed off may be considered to be a finished article of commerce ortube, although it is also adapted for further treatment in a reducingmill either with or without reheating. If desired, the blank may bepassed toward the left along the conveyor 20 directly into a reducingmill 22 illustrated diagrammatically in Figure 3. Such mill may be ofany desired or well known construction and by successive passes reducesthe diameter of the blank. The reducing mill shown in Figure 3 comprisessuccessive stands of rolls, each stand comprising a pair of cooperatingreducing rolls mounted to rotate about parallel axes lying in a planeperpendicular to the axis of the blank, the axes of the rolls ofsuccessive stands being alternately criss-crossed.

Figures 2A and and 2B are complementary and are adapted to be fittedtogether along the line X-X at the left hand side of Figure 2A and theline X-X at the right hand side of Figure 2B.

These figures show a modified mill construction. As in Figure 1, thepush bench is indicated diagrammatically at 23, being represented by itsrunout table, and the mandrel having the blank thereon passes directlyto a reeler 24 having reeling rolls 25 for loosening the blank on themandrel to facilitate stripping. The respective rolls 25 are mountedupon cross shafts 26 driven by a mot-or 21 through gearing 28 anddriving connections 29. A guide 30 and a roller conveyor 3| assist inproperly guiding and advancing the mandrel and blank.

The mandrel having the reeled "or loosened blank thereon passes towardthe right on a roller conveyor 32 to a position at which it is lifted bythe fingers 33 and moved laterally over the rails 34 to a rollerconveyor 35 cooperating with a stripper 36, similarly to the embodimentof Figure 1. The stripped blank is lifted from the conveyor 35 byfingers 31 and transferred onrails 38 to a roller conveyor 39 whichfeeds it to a saw 40, also similarly to the embodiment of Figure 1. Thestripped and sawed blank passes to the left upon a roller conveyor 4|.

At this point the blank may be reheated in a reheating furnace 42 or, ifat a proper temperature, may by-pass the heating furnace by any suitableconveying mechanism (not shown), and is fed toward the right on a rollerconveyor 43. An elongating mandrel 44 is introduced into the blank andthe blank with the elongating mandrel therein is removed from theconveyor 43 by fingers 45 and passes laterally along rails 46 to aroller conveyor 41 from which it is moved toward the left through anelongator 48, which, together with its associated mechanism, may besubstantially a counterpart of the elongator 3 of Figure 1. From theelongator 48 the blank having the mandrel 44 therein passes toward theleft on a runout table 49 and the elongator mandrel is withdrawn. Thismay be done by an extractor similar to the extractor 36. The elongatormandrel may be of substantially smaller size than'the push benchmandrel, resulting in relatively heavy reduction, both in diameter andin wall thickness, and also relatively great elongation in theelongator. i

The blank on the conveyor 49 may be consldered to be a finished articleof commerce or tube, although it is .also adapted for further treatmentin a reducing mill either with or without reheating, as in the case ofthe blank emerging on the conveyor 20 in Figure 1. The reducing millshown in Figure 3 may form a part of the mill of Figures 2A and 23,receiving the blank from the conveyor 49. Thus relatively small thinwalled tubing may be manufactured at remarkably low cost and at highspeed. From a comparatively short blank of relatively great wallthickness emerging from the push bench a tube many times as long and ofmuch less diameter and wall thickness may be produced. ,The economies ofthe push bench are obtained, yet products heretofore ordinarilymanufactured on a piercing mill are made.

While I have shown and described certai present preferred embodiments ofthe inventio it is to be distinctly understood that the same is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims.

I claim:

1. A process for the manufacture of tubes, comprising thinning andlongitudinally elongating a blank over a mandrel in a push bench, andthereafter simultaneously-further thinning and longitudinally elongatingsaid blank over said mandrel and loosening said blank with respect tosaid mandrel while maintaining the exterior of the blank substantiallysmooth.

2. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, and thereafterelongating said blank over a mandrel between cross rolls.

3. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, stripping the blankfrom said mandrel, and thereafter elongating said blank over anothermandrel between cross rolls.

4. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, stripping the. blankfrom said mandrel, inserting another mandrel into said blank, andelongating said blank over said second mentioned mandrel by passing theblank and mandrel between rolls.

5. A process for the manufacture of ,tubes, comprising thinning andelongating a blank over a mandrel in a push bench, stripping the blankfrom said mandrel, inserting into the stripped blank another mandrel ofless diameter than said first mentioned mandrel, and elongating saidblank over said second mentioned mandrel by passing the blank andmandrel between rolls.

6. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, and thereaftersimultaneously spinning and elongating said blank over a mandrel.

7. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, removing said mandreland blank from the push bench, thereafter further elongating said blankover a mandrel, and

thereafter reducing said blank in a reducing mill.

8. A processfor the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, thereafter furtherelongating said blank over a mandrel between cross rolls, and thereafterreducing said blank in a reducing mill.

9. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, reeling the blank toloosen it from the mandrel, stripping the blank from said mandrel,inserting into the stripped blank another mandrel, thinning andelongating the blank over said second mentioned mandrel, and thereafterreducing said blank in a reducing mill.

10. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, stripping the blankfrom said mandrel, inserting into the stripped blank another mandrel ofless diameter than said first mentioned mandrel, thinning and elongatingthe blank over said second mentioned mandrel, and thereafter reducingsaid blank in a reducing mill.

11. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, stripping the blankfrom said mandrel, heating the blank, inserting into the blank anothermandrel, and elongating the blank over said second mentioned mandrel bypassing the blank and mandrel between rolls.

12. A process for the manufacture of tubes, comprising thinning andelongating a blank over a mandrel in a push bench, stripping the blankfrom said mandrel, inserting into the stripped blank another mandrel ofless diameter than said first mentioned mandrel, thinning and elongatingthe blank over said second mentioned mandrel between cross rolls, andthereafter reducing said blank in a reducing mill.

13. A process for the manufacture of tubes, comprising thinning and amandrel in a push'bench, and thereafter thinning and elongating saidblank over a mandrel while rendering the same relatively loose thereon.

14. Apparatus for tube manufacture, comprising a push bench having diesand a mandrel and an elongator provided with cross rolls between which amandrel. with a blank thereon is adapted to pass to further elongate theblank after a precedent thinning and elongation in the push be'nch.

15. Apparatus for tube manufacture, comprising a push bench having diesand a mandrel, a stripper, means for inserting another mandrel into astripped blank after a precedent thinning and elongation in the pushbench, and an elongator provided with cross rolls between which saidsecond mentioned mandrel with the blank thereon is adapted to pass.

16. Apparatus for tube manufacture, comprising a push bench having diesand a mandrel, an elongator having cross rolls and a reducing mill, saidpush bench, elongator and reducing mill being constructed and arrangedto successively operate on a blank.

1'7. Apparatus for tube manufacture, comprising die means for thinningand longitudinally elongating a blank over a mandrel and means forfurther thinning and longitudinally elongating said blank over a mandrelwhile rendering the same relatively loose thereon and maintaining theexterior of the blank substantially smooth.

18. Apparatus for tube manufacture, comprising a push bench having diesand a mandrel, a

elongating a blank over reeler, a stripper, means for inserting anothermandrel into a stripped blank after a precedent thinning and elongationin the push bench, and an elongator provided with cross rolls betweenwhich said second mentioned mandrel with the blank thereon is adapted topass.

19. Apparatus for tube manufacture, comprising a push bench having diesand a mandrel, a stripper, means for supplying another mandrel forinsertion into a blank, and an elongator through which said secondmentioned mandrel with the blank thereon passes.

20. Apparatus for tube manufacture, comprising a push bench having diesand a mandrel, a stripper, means for supplying another mandrel forinsertion into a blank, an elongator, and a reducing mill.

CARL W. LITTLER.

